Sound projecting apparatus



Aug. 30, 1932. 1,875,171

AAAAAAAAAAAAAAAAAAAAAA US l N V E N T O R5 L.A.SpI -gue and C. 1 717016012 IY TTTTTT EY Patented Aug. 30, 1932 I LE ROY A. SPRAGUE AND CHARLES F. DOBSCH, F MODESTO, CALIFORNIA SOUND PROJECTING APPARATUS Application filed August 14, 1929. Serial No. 385,917.

This invention relatesto sound projection, duce a simple and inexpensive device and and particularly to an apparatus to be emyet one which will be exceedingly effective ployed in conjunction with a loud speaker for the purpose for which it is designed. such as is used in radio and other sound am- I These objects we accomplish by means of plifying apparatus for the purpose of prosuch structure and relative arrangement of j ecting the sounds emanating from such parts as will fully appear by a perusal of the speakers a greater distance than is possible following specification and claims. with the loud speaker alone. In the drawing similar characters of refe principal object of our invention is erence indicate corresponding parts in the to provide an apparatus, adapted to be several views: 00 mounted in connection with any standard Fig. 1 is a perspective view of our improved loud speaker of the dynamic or cone type, so apparatus. arranged that practically all sound Waves Fig. 2 is a vertical cross section of the same. 7 released on the outside or back of the speaker Referring now more particularly to the 15 cone will be utilized and projected into the characters of reference on the drawing, the atmosphere in a common direction with those apparatus C mprises a casing or box 1, prefissuing from the interior of the speaker. Not erably square in form and somewhat shallow only therefore is the total volume of sound in depth relative to its face area. The sides increased but such inside and outside waves of the box may be of wood or other relatively J) are projected in such synchronized and har- Vibrationless material, while the front and monious relation to, each other as to cause back of the xare panels2and .3 respectively th ound to carry much further, with a relaof a material having definite sound insulating tively slight decrease in volume, than has or deadening characteristics as to sound previously'been thought possible, and with Waves or vibrations of a certain character 25 no decrease in the clarity of the tones. only. The parts of the box are rigid and ur improved projection apparatus is tightly fit with each other. Arelatively deep therefore very adaptable for use in theaters outwardly flaring flange 4 extends about th showing talking pictures, since the'voices or box and'projects from the front of the same. music are distributed with practically equal If desired the bottom member of this flange volume and clearance to all parts of the may be flat instead of flaring so as to enable theater. the device to besupported on top of a flat sur- The apparatus is also admirably adaptable face of any desired character.

j for the use of speakers or orators at large A centrally located orifice 5 1S out in the gatherings, whether indoors or outdoors, who front panel 2, which orifice 18 substantially have heretofore lacked any effective means the same size as the mouth of the cone 6 of a for projecting their voices so as to reach or n rd l d speaker 7, Which speaker is 10- be intelligible to the entire audience. Gated inside the box and 1S S8t so that the h r tu i al o v r uitabl f r month of the cone has an airtight fit with or for other purposes; and being capable of Central opening and preferably toward the being made as a, portable device it is also use corners of the ox are other openings 8. 1 f unti g on i' hi 1 Thi These other openings are all equal size but are feature also makes the device aluable for smaller than the central opening t0 an extent advertising purposes, since sounds emanatsuch that the combined area of these openings ing from the apparatus can be clearly heard is substantially equal to that of the centra'i a considerable distance from the apparatus opening. These openings 8 merely lead to and with great clearness even above the orthe interior of the box and are not arranged dinary street or traffic noises. in direct connection with the loud speaker. 50 A further object of the invention is to pro- If the location of the apparatus demands, the

' tically as many such waves on "time spacing between the r iliary openings posed relative to the main central opening the various openings may be covered by vibrationless screening 9so as to prevent anything being possibly thrown into the box.

In the operation of the loud speaker the amplified sound waves as generated therein are transmitted to the cone and there are practhe outside or back ofthe cone as there are on the inside. Ordinarily such outside waves are lost since they are not concentrated and projected in y perti l di e t oni d ly o e the inside of the cone are utilized; so that the speaker does not operate to .its. .capacityor full eificiency.

With our apparatus however arranged in connection with such a speaker theseoutside 'waves' are thrown against the back panel 3. and "then outwardly: and forwardly through theopenings 8 in the same direction as the V waves projecting directly from the inside of the'cone through the central opening b. "The volume of sound projecting in a definite direction from the speaker is therefore prac- "tically doubled over what is usually obtained. At the same time there is ofcourse a slight variation inthe time betweeni the projection of the two sets ofwaves, since theoutside or back waves must travel to the back panel and then to the front panel before leaving the apparatus whereas the inside waves leave the apparatus directly or without any initial deflectionof direction. This variation of time is so slight as not to be noticeable to the ear, and also the sound wavesappear to be perfectly synchronized. The actual result of this arrangement however is 'tlgat thisslight sets 0 the duration of. the waves as'a wholeto be filled out or lengthened, so that 'thesoun'd carries without much decrease in volume for a considerable distance. f V i The principle involved may be considered something similar to that had with the production of an echo, except that in thiscase, as above stated, the lapse of time between the two sets of sound .waves is so slight that no "appreciable echo efiect is obtained. The aux- 8. being symmetrically dissounds all mergeand combine evenly and the fact that the combined area of these auxiliary openings is the same as that of the mainopening gives them equal sound Carrying capacity.

Owing to the use ofsound deadening material for thefront and back box panels against which the sound waves impinge, no vibrations are set up within the box by-such' waves to interfere with the clarity of the tones projected therefrom. auxiliary openings also prevent the inevitable vibration of the cone, which is set up with the action of the sound waves, from tending to compress the air within the box such aswould set "up drumming "or similar noises in the am V 'theexpense of 7 device as substantially fulfillsthe objects waves causes v ing, in combination with of the cone, and same volume.

. ing, in combination scone. The prov1s1on. of these ing cone of a loud speaker, abox speaker is'enclosed,

is to be operated. This is because deepening the box somewhat increases the depth of the tones and the distance to which they may be projected to attain the desired long range properties of the apparatus; while making the box more shallow sharpens the'tones at the extreme long range.

, As pre ipilf yistated, ztheranels'a e Sound deadening or absorbing to vibrations of a certain" character only. ,The vibrations in question are those of high frequency and consequently high-pitched or nasal tones,

which are absorbed. The

low frequencyv afiected, and. are, thrown from the back paneland fthrough the openings with practicallyundiminished volume. This increases the carrying range andvoljume of these low frequency tonesrelative to the high frequency tones, vwitho,ut 'also increasing the volume of the high-pitch tones, so that the two are substantially equalized.

j The usualpredominance of, thehigh pitch tones, and which causes the. sounds emitted from loud speakers-to be of squawky? or na sal character as a whole, is thus eliminated.

' From the foregoing description it. will .be readily seen; that wehave produced sucha of the invention set forthjherein. 'jj While this specificationsets forth in 'detail the present, and preferred construction ofthe device, still in practice such deviations from such detail maybe resorted to. as do not-form a-jdeparture from the spirit of the invention, as defined by the appended claims. f

Having thus described ourinvent-ion what weclaim-as new and=useful and desire to secure by Letters Patent is:

1, A [sound projecting. apparatus compristhe. sound projecting cone of a loud-speaker, outside surface of the-cone in the same direction as those vproj ecting from the interior I with approximately .the

. 2. A sound projectingapparatus comprisr'wit'h the sound proj ecting cone of a,loud-speaker,a.means for catching the sound waves thrown fromthe back surface of the cone and proj ecting them forwardly about and inrispaced relation tothe 3. -A' ing, in combinatlon, withlthe. sound projectin whichthe t 'hq j ri gs n Op 0 a means for proecting the soundawaves emanating from-the sound.projecting. apparatus comprisbe varied within brations, I or those of low-pitch .tonal qualis ties, are not ing in its ,front wall with which the mouth being located centrally of the area of the front wall.

6. A device as in claim 3, in which the combined areas of said other openings substantially equal that of the first named openmg.

In testimony whereof we aflix our signatures.

LE ROY A. SPRAGUE. CHARLES F. DORSCH. 

